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The optimization of the exhaust port shape for best mass flow is an excellent opportunity to improve fuel economy, emissions, and knock sensitivity of internal combustion engines (ICE). This is valid for many different types of combustion systems including gasoline, alcohols, alternative fuels such as compressed natural gas (CNG) or hydrogen, and e-fuels. Nowadays, so-called cylinder-head integrated exhaust manifolds (IEM) guide the exhaust gas from the combustion chamber to the turbocharger. This specific design requires lots of strong bends and turnings of the exhaust ports in very narrow space, since they need to be guided through a labyrinth of bolts, water cores, and oil passages. In fact, this challenges the avoidance of increased pressure drops, reduced mass flow rates, and deterioration of port flow efficiencies. The optimization of the individual port by computational fluid dynamics (CFD) is a proper means to minimize or even eliminate these drawbacks.